1. Field of the Invention
The present invention relates to systems and methods for the trapping of liquids or solids which may be present in a breath prior to the breath being presented to a breath testing device.
2. Description of the Related Art
For the purposes of public safety on the roads and elsewhere, there is a need to make sure that individuals are not operating potentially dangerous machines (such as automobiles) while they are impaired by the effects of alcohol consumption. To try and prevent people from driving drunk, most states have enacted laws which impose fines or other criminal penalties if individuals have a breath or blood alcohol level above a certain amount. In order to effectively enforce these laws, it is necessary to be able to measure the alcohol concentration of a human's breath and compare the results against legal limits. There are a variety of measuring instruments used for determining the concentration of alcohol in human breath ranging from small hand held devices to larger bench top units and machines built into cars or certain machinery. Since a determination of breath alcohol above the legal threshold can result in criminal penalties, loss of a job, or other sanctions, the accuracy of these instruments is paramount.
In addition to accuracy, there are also obvious concerns about the sanitation and reliability of evidentiary breath testers. Since the machines need to take a sample of the subject's breath, they are necessarily exposed to whatever else may be in the subject's breath or mouth at the time the measurement is taken. Liquid droplets or solid particles which may be in the breath can present a myriad of problems for an evidentiary breath tester. Specifically, they can result in unsanitary conditions if they remain in the breath tester and could potentially be inhaled by a later subject. They can also result in microbial growth or other fouling of the testing instrument's sampling mechanism. Similarly, if such particles get into the testing chamber of the tester, they can potentially damage the chamber or make the tester require service in order to remove the contamination and ensure that the device operates in a reliable and accurate manner.
A breath sample generally cannot to be taken without the human subject cooperating. Specifically, the human subject generally must provide the sample of breath for analysis, generally by exhalation into the breath testing apparatus. This is usually done in the form of a “blow” by the subject, i.e. a forced exhalation against backpressure into a tube or manifold. From the breath in the tube, a sample is then taken by the tester in order to determine the alcohol concentration in the subject's breath.
Generally, the portion of this tube that enters the subject's mouth is generally a low cost, replaceable, and disposable mouthpiece. The device is disposable for sanitary reasons so that there is a reduced chance of germs, or other undesirable components of a subject's breath, being transferred between different people. It is low cost and replaceable to meet the requirements of being affordable for regular use of the breath tester when the breath tester is to be used on multiple subjects.
Depending on the type of breath testing apparatus used, some tubes or devices may contain check valves that keep a subject from sucking back air from the tube. This check valve can provide for improved sanitation by inhibiting the subject from pulling air, and any suspended material, from the testing device. Certain devices may also have check valves to provide for increased accuracy as alteration in the nature or speed of the flow could produce an inaccurate result and to inhibit the subject from trying to fool the machine by pulling fresh air through the machine and into their lungs or reducing a sample size by pulling back on a sample, instead of fully exhaling into the machine.
Most breath testing devices utilize exhaled breath vapor, and specifically deep lung vapor (alveolar breath), to determine breath alcohol level. This breath vapor generally presents an accurate representation of blood alcohol level and therefore is most desired in breath testing. However, to obtain such a deep lung breath, a human user needs to generally breathe a significant amount of air into the tube (so as to clear air from the mouth and upper lungs) and as part of doing so will often force liquid or solid particles into the tube as well due to the force of the breath. This can include liquid droplets of saliva or other materials in the mouth or throat or particles of food or other solid substances.
These problems can be further exaggerated in inebriated subjects as when they blow into alcohol breath testers, there is an increased propensity for saliva, in the form of drool or slobber, to be delivered along with the breath during a subject blow. This can both increase the likelihood that some material is projected, as well as the total amount of material projected for an average subject. Sometimes, inebriated subjects, who have impaired thinking, will even try to blow spit, phlegm, nasal fluids, or solids into a breath tester, thinking that this might affect the instrument in some way that will be of benefit to themselves. A very inebriated subject may even inadvertently vomit or otherwise project certain stomach contents into the tube.
Traditionally in certain types of testing devices, the tube has done very little to prevent these problems as they have very little effect on most sampling devices. In machines where liquid or solid projection can cause increased problems, certain types of spit traps do exist. FIG. 1 provides an example of mouthpiece spit trap design of the prior art consisting of various “baffle” structures. These are meant to provide a more tortuous path for the breath and include surfaces that are meant to frictionally hold back liquids and solids, or create eddies to trap liquids, all the while letting vapor pass through. These designs are effective to an extent, but only at lower breath flow rates. At higher flow rates, these mouthpieces often perform poorly as the stronger breath tends to sweep particles and droplets along with it due to the increased pressure it provides.
As a result, measuring instruments utilizing such spit valves are often designed with internal restrictions designed to increase backpressure during a subject blow and therefore purposely keep flow rates low, thus increasing the effectiveness of the baffle-type mouthpiece designs to serve as traps. The problem with this is that these instruments become “hard to blow” as subjects have to blow hard against this backpressure and it can become quite uncomfortable and unnatural for the subject.
Especially when a subject is potentially inebriated, one prefers not to introduce factors into the process that make it more difficult to get a proper breath sample and therefore designs which increase backpressure can be considered to simply trade one problem for the other. While they may reduce material projection into the device, they may simultaneously have the user produce a less desirable sample breath or have trouble producing a useable sample at all. Because backpressure changes can create problems, there are international bodies that regulate the maximum backpressure allowed in a measuring instrument. However, these regulations generally only regulate the maximum backpressure which can be used in any instrument to make sure that the instrument will obtain a reasonable sample. Individual manufacturers may use any backpressure up to this amount and, therefore, there may be different backpressures between different devices. So, in the case of universal mouthpieces which are deigned to operate on a variety of different instruments where manufacturers may internally select to use different backpressures to provide for their own internal accuracy, these have to be designed to operate across a variety of instruments with a variety of backpressures. In the case of baffle systems such as that of FIG. 1, this can lead to a mouthpiece which is effective with one device, but ineffective in another.